The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The spine is a flexible column formed of a plurality of bones called vertebrae. The vertebrae include a hollow cavity and essentially stack one upon the other, forming a strong column for support of the cranium and trunk of the body. The hollow core of the spine houses and protects the nerves of the spinal cord. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibrocartilaginous bodies. Each vertebra includes upper and lower endplates formed from harder compact bone than the softer cancellous bone of the interior of the vertebra.
The intervertebral bodies, also known as intervertebral discs, include a fibrous ring filled with pulpy material. The discs function as spinal shock absorbers and also cooperate with synovial joints to facilitate movement and maintain flexibility of the spine. When one or more discs degenerate through accident or disease, nerves passing near the affected area may be compressed and consequently irritated. The result may be chronic and/or debilitating neck and/or back pain due to these spinal disorders.
Various methods and apparatus have been designed to relieve such back pain, including spinal fusion using an interbody spacer and suitable graft using techniques such as anterior interbody fusion, posterior interbody fusion, or transforaminal interbody fusion surgical techniques. The implants used in-these techniques are placed in the intervertebral disc space between adjacent vertebrae of the spine. Bone graft material may be placed within the spacers to facilitate bone growth between the adjacent vertebrae. Many times an exterior plate and/or screws are used in conjunction with the implant to hold the adjacent vertebrae while the fusion occurs.
Ideally, the interbody spacer should stabilize the intervertebral space and allow fusion of the adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the interbody spacer should have sufficient structural integrity to withstand the stress of maintaining the space without substantially degrading or deforming and have sufficient stability to remain securely in place prior to actual bone in-growth fusion.
One significant challenge to providing fusion stability (prior to actual bone ingrowth fusion) is preventing spinal extension during patient movement. Distraction of the vertebral space containing the fusion graft may cause the interbody spacer to shift or move disrupting bone ingrowth fusion and causing pain. An exterior plate is often used with the interbody spacer to hold the adjacent vertebrae while the fusion occurs. There remains a need for an interbody spacer capable of holding the adjacent vertebrae steady during fusion without the use of external plates.